1. Field of the Invention
The present invention relates in general to vehicular seat position adjusters, and more particularly, to vehicular seat lifters which lift and lower a vehicular seat to a desired height position for providing a seat occupant with a comfortable sitting posture.
2. Description of the Prior Art
In order to clarify the task of the present invention, a conventional vehicular seat lifter will be described with reference to FIG. 4 of the accompanying drawings.
The seat lifter is designated by numeral 3a, which mounts thereon a seat assembly. The seat assembly comprises a seat cushion 2 mounted on the seat lifter and a seatback (no numeral) mounted on a rear end of the seat cushion 2.
The seat lifter 3a comprises a rectangular base member 4 mounted on a vehicle floor 1. Front and rear pivot shafts 8a and 8b extend across opposed side wall portions of the base member 4. Each pivot shaft 8a or 8b has left and right crank levers 5a and 5b secured thereto. Each crank lever 5a or 5b includes a downwardly extending arm and a rearwardly extending arm. The left crank levers 5a and 5a on the front and rear pivot shafts 8a and 8b are pivotally connected at their downwardly extending arms to front and rear ends of a left link 9a, and similar to this, the right crank levers 5b and 5b on the front and rear pivot shafts 8a and 8b are pivotally connected to a right link 9b. The rearwardly extending arms of the four crank levers 5a and 5b each have a bracket 6a or 6b pivotally connected thereto. These four brackets 6a are bolted at their bent ends to the seat cushion 2. Denoted by numeral 7 is a bolt opening of each bracket 6a or 6b, through which a bolt (not shown) for connecting the bracket and the seat cushion 2 passes.
When the pivot shafts 8a and 8b are rotated about their axes by a drive means (not shown), the rearwardly extending arms of the crank levers 5a and 5b and thus the brackets 6a and 6b pivotally connected to the arms are raised or lowered relative to the pivot shafts 8a and 8b. Thus, the seat cushion 2 on the brackets 6a and 6b is moved upward or downward to a desired height position.
However, due to its inherent construction, the seat lifter has the following drawbacks.
That is, the work for assembling or mounting the seat assembly to the brackets 6a and 6b is difficult or at least troublesome. In fact, positioning of each bracket 6a or 6b (more specifically, positioning of the bolt opening 7 formed therein) relative to given portions of the seat cushion 2 is very difficult because the brackets are liable to swing unstably before they are bolted to the seat cushion 2. If the mounting of the seat cushion 2 to the brackets 6a and 6b is carried out with a poor position matching therebetween, smooth operation of the seat lifter 3a is not expected. If a special jig is used for achieving the position matching, production cost of the seat lifter is increased.